A radio communication system that does not need a license in an industry-science-medical (ISM) band has been widely used. A communication quality of the radio communication is deteriorated by receiving interference waves from other communication and other radio system using the same time and the same frequency, an electric apparatus such as a microwave, and an obstructer. Therefore, it is necessary to improve an interference resistance performance. As a method for improving the interference resistance performance, for example, Patent Literature 1 discloses a method for randomly inserting null symbols by using the orthogonal frequency division multiplexing (OFDM) method and measuring an interference power by using the null symbols.